Dragging rows onto the queue panel now lands them AT the pointed slot
(insertion line included) instead of appending: add_track + move_track
compose the position locally (QueueManager has no insert-at-index and
the manual-block adds would corrupt manual_next_count), and the
QConnect controller path routes through CtrlSrvrQueueInsertTracks'
insert_after so the position survives to the peer. Multi-row drops keep
their own order. Dropping onto an EMPTY queue raises a one-shot
'start playing?' prompt rather than hijacking a running queue or
leaving the user one click short.
cc
vicrodh
c198afb33c